Variable resistance control



Jan. 2 1968 3, RT BE|TNER A 3,362,003

VARIABLE RESISTANCE CONTROL 2 Sheets-Sheet 1 Filed Aug. 51, 1964 m 5 R mmm NEN EBE R IS m R N HM MmCS w Q QMW Q 0M 2 H 2 .m. C 0 Ms M Q3 \8 II 5 a a O D 7 36 9 5% M M 445 2 WILLIAM L. HAYES, JR E BY ATTO'RN y 2 5 c. R. BEITNER ETAL 3,352,003

VARIABLE RESISTANCE CONTROL 2 Sheets-Sheet z Filed Aug. 31, 1964 INVENTORS CHARLES 'R. BEITNER STANLEY O. BENDER WILLIAM L. HAYES JR.

BY WWW AT TORNE Y United States Patent Filed Aug. 31, 1964, Ser. No. 393,237 Claims. (Cl. 338-174) The present invention relates to electrical controls, and, more particularly, to an improved variable resistance control of the type employed in a hearing aid and the like.

Various designs of hearing aids are available depending upon the particular requirements of the individual. A person, for example, wearing glasses, can have the hearing aid mounted in one of the temples of a pair of eye glasses. And, if the person does not wear glasses, the hearing aid can be encapsulated into an ear mold insertable into the inner semicircular canal of an ear or the hearing aid can be supported behind the ear and connected to an ear mold. The hearing aid, therefore, is constructed in such a manner as to be protected as much as possible from body acids, grease, moisture, perspiration, dust and the like. Otherwise, the hearing aid quickly becomes defective and inoperable. Based on records of repairs made to hearing aids during the past years, the portion of the hearing aid that generally becomes inoperable is the volurne control, i.e., the variable resistance control. This is rather obvious since the control is frequently adjusted, and it is difficult to seal completely the inside of the control from the rotatable knob. It would, therefore, be desirable to provide an improved variable resistance control wherein the operation thereof is not affected by atmospheric and other environmental conditions.

Whenever a variable resistance control is subjected to dynamic forces such as usually encountered when the control of a hearing aid is carried by a person, it is necessary that the rotational torque of the control be sufficiently high to prevent inadvertent movement of the shaft causing frequent adjustment of the control. Most controls employ internal biasing means, e.g., a preformed spring compressed inside of the housing exerting the desired force for obtaining a high rotational torque. As the physical size of a variable resistance control is decreased, it is however, more diflicult to calculate the force exerted by the biasing means and determine the rotational torque of the control unless each part having an effect upon the biasing means is inspected before assembly and the parts are selectively assembled. Some of the difficulties result from using parts having standard manufacturing tolerances. Such tolerances cannot be decreased since competition demands that costs be kept at a minimum. Complete inspection of all the parts does not, however, insure that the rotational torque of all the controls will be satisfactory. It is usually necessary to disassemble the rejected controls before the force exerted by the biasing means can be altered since the biasing means is disposed inside of the housing. It would, therefore, also be desirable to provide external means for adjusting the force exerted by the biasing means thereby permitting adjustment of the rotational torque of a variable resistance control in a simple and facile manner after the control is assembled.

Generally, sealed variable resistance controls cannot be taken apart for correction of a defect detected during electrical inspection of the assembled control without destroying the housing thereof. It would, therefore, be desirable to provide a variable resistance control with sealing means of the pressure type in order that the control can be readily taken apart.

Accordingly, it is an object of the present invention to provide a new and improved variable resistance control having the various desirable features set forth above.

Another object of the present invention is to provide an improved variable resistance control having a rotatable knob slideably keyed to the driver of the control for permitting adjustment of the rotational torque after the control is assembled.

An additional object of the present invention is to provide a variable resistance control employing a single biasing means for altering the rotational torque of the control and for pressure sealing the housing of the control.

A further object of the present invention is to provide a variable resistance control having an annular bead biased against a flexible insulating membrane for sealing the control.

Still another object of the present invention is to provide an improved variable resistance control wherein the axial distance between the driver and the externally rotatable knob of the control may be altered for obtaining the proper rotational torque.

A still additional object of the present invention is to provide a variable resistance control wherein the cover sealing the open end of the housing is provided with a pair of cars for mounting the control to a panel.

A still further object of the present invention is to pro-' vide an improved vairable resistance control having biasing means mounted externally of the housing of the variable resistance control for acquiring the appropriate rotational torque.

Further objects and advantages of the present invention will become apparent as the following description proceeds, and the features of novelty characterizing the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Briefly, the present invention is concerned with a variable resistance control comprising a housing defined by a cup-shaped molded member rotatably supporting a driver provided with a threaded bore. The terminals of the control are molded into the base of the cup-shaped member for precise location of the terminals in the housing. An apertured cover closes the open side of the cup-shaped member and a flexible insulating membrane disposed on the inner surface of the cover engages an annular bead of the driver for sealing the interior of the housing from the foreign elements. A resistance element is mounted in the housing, and a contactor carried by the driver wipes the resistance element intermediate the ends thereof. A knob rotatably supported in the aperture of the cover is keyed to the driver. Interposed between the outer surface of the cover and the inner surface of the knob is a biasing means such as a washer biasing the annular bead of the driver against the flexible insulating membrane disposed on the inner surface of the cover. A screw threadedly engaging the threaded bore of the driver secures the knob to the driver, and adjustment of the screw controls the biasing force of the annular bead against the membrane for altering the rotational torque of the control.

For a better understanding of the present invention, reference may be had to the accompanying drawings wherein the same reference numerals have been applied to like parts and wherein:

FIGURE 1 is an isometric view of a sealed variable resistance control built in accord with the present invention;

FIGURE 2 is a sectional view taken on line IIII of FIGURE 1;

FIGURE 3 is a perspective view of the variable resistance control with portions cut away to show the internal construction of the control; and

FIGURE 4 is an exploded view of the control of FIG- URE 1.

Referring now to the drawings, there is illustrated an improved variable resistance control, generally indicated at 10, comprising a housing 11 defined by a cup-shaped member 12, and an apertured cover 20 closing the open side of the cup-shaped member 12.

Considering first the cup-shaped member 12, it comprises a cylindrical Wall 12a and an integral base 12b preferably molded of any suitable nonconductive material such as phenol-formaldehyde or polyester molding compounds. Terminals 13, 14, and 15 are molded into the base 12b of the cup-shaped member 12 in a suitable manner, and, therefore, the bottom portion of the housing 11, where the terminals are located and extend outwardly therefrom, is completely sealed. The terminals 13 and 15 are electrically connected to an arcuate resistance element 16 and the terminal 14 is integrally connected to a collector ring 17 disposed in the center of the inner bottom portion of the base 12b Molding of the terminals into the base 12b of the cupshaped member 12 also facilitates accurate positioning of the terminals in the cup-shaped member 12. To position the terminals properly in the cavity for molding the cupshaped member 12, it is preferable that the terminals be secured to a not-shown terminal carrier strip or the like. The terminal carrier strip is blanked out with groups of properly spaced terminals 13, 14, and 15 and, by using the same locating pins employed for blanking the terminals in the molding operation, precise positioning of the terminals in the base of the cup-shaped member 12 is obtained. After the cup-shaped member 12 is molded to the group of terminals, the terminals are severed from the terminal carrier strip. The collector ring 17 is provided with a peripheral lip or downwardly turned flange 17a, as best seen in FIGURE 2 of the drawings, for anchoring the end opposite the terminal end of the collector ring 17 in the base 12b of the cup-shaped member 12.

Encircling the collector ring 17 is an arcuate cavity 120 in the inner bottom portion of the base 12b receiving the resistance element 16, the ends of the cavity being disposed on opposite sides of the terminal 14 integrally connected to the collector ring 17. The walls of the arcuate cavity 120 are coated with a suitable electrically nonconductive epoxy cement for bonding the resistance element in the arcuate cavity 120. The arcuate resistance element 16 comprises a laminated phenolic substrate 1611 having a resistance path 16b deposited on one side thereof and, before the resistance element 16 is nestedly disposed in the arcuate cavity in the inner bottom portion of the cupshaped member 12, silver-laden epoxy cement is coated around the ends of the resistance element 16. The ends of the 'arcuate resistance element 16 overlie the inner ends of the terminals 13 and 15, and the silver-laden epoxy cement firmly bonds the ends of the resistance element 16 to the terminals 13 and 15 and also electrically connects the resistance path 16b to the terminals 13 and 15. It is to be understood that the substrate 16a of the resistance element 16 need not be limited to a laminated phenolic and can be of a ceramic material such as alumina or steatite having a conductive glass resistance path deposited on a surface thereof.

As illustrated in the drawings, the cover 20 closes the open side of the cup-shaped member 12. In order to prevent relative rotation between the cover 20' and the cup-shaped member 12, the cylindrical side wall 12a is provided with a pair of spaced peripheral shoulders 12d and 12e (see FIGURES 1 and 4) defining a pair of diametrically opposed notches 19a. Preferably and as shown in the drawings, a pair of rearwardly extending arms 21 integrally connected to the cover 20 are disposed in the notches 19a. Suitable tabs 22 forming a part of the arms are folded against the outer surface of the base 12b of the cup-shaped member 12 for fixedly securing the cover 20 to the cup-shaped member 12. Should a defect in the control 11) exist after the control is assembled and electrically tested, it is merely necessary to unfold the tabs 22 to take the control apart for making the proper correction without damaging the control. To prevent the tabs 22 from interfering with the mounting of the variable resistance control 10 against the amplifying board of a hearing aid or the like, a pair of recesses 12; is provided in the outer surface of the base 12b. For the purpose of facilitating mounting of the variable resistance control 10, a rearwardly extending mounting ear 23 is preferably integrally connected to each of the arms 21. It is, therefore, merely necessary to insert the terminals 13, 14, and 15 and the mounting ears 23 into suitable not shown slots provided in the not shown amplifying board and fold over the end portions of the ears 23 for securing the control 10 to the board. A pair of diametrically opposed locating pins 24 extending outwardly from the recesses 12 in the base and receivable in suitable not shown openings in the amplifying board accurately locates the variable resistance control 10 thereon.

It will be appreciated that means must be provided inside of the housing 11 for wiping a contact button intermediate the ends of the arcuate resistance element 16. To this end, a contactor 30 of good electrically conductive resilient material is fixedly secured to a brass driver 40 rotatably mounted in the housing 11. As best seen in FIG- URE 4 of the drawings, the contactor is provided with a slot or perforation 31a for separating and spacing a pair of contact arms 32a and 321) from a center portion 30a of the contactor 31 The free ends of the contact arms 32a and 32b are provided with rounded contact buttons 33a and 33b, and the arms 32a and 32b are preformed out of the plane of the center portion 30a so as to be biased against the resistance path 16a of the arcuate resistance element 16 as best shown in FIGURE 3 of the drawings. The portion of the contactor 30 diametrically opposite to the contact arms is provided with a perforation 31b so as to define a pair of spaced inwardly extending collector ring paddles 34a and 34b. By extending the end of the paddles inwardly of the outer periphery of the collector ring, the free length of the paddles is increased, and, accordingly, the spring range of the collector ring paddles 34a and 34b is increased substantially.

In order to constrain the contactor 30 to rotate with the driver 40, the contactor 30 is provided with a pair of forwardly extending locating tabs 36 received in a pair of diametrically opposed slots 41 on the periphery of the driver 40. The perforation 31b of the contactor 30 is also provided with a circular portion engaging the outer surface of the shoulder 42 extending rearwardly of the driver 40. The outer edge 42a of the shoulder 42 is staked over the circular portion of the perforation 31b to secure the contactor 30 to the driver 40.

Preferably and as best illustrated in FIGURE 2 of the drawings, the driver 40 is provided with a rearwardly extending hollow spindle 43 journaled in an opening 17a provided in the collector ring 17. The spindle 43 also extends into a cylindrical cavity 12g provided in the base 12b and axially aligned with the opening 17a. The other end of the driver 40 is rotatably supported in the central aperture 20a of the cover 21) and operably connected to the hub 51 of a knob 50.

In accord with the present invention, the other end or front portion of the driver 40 is slideably keyed to the knob 50 by means of a pair of forwardly extending legs 44 extending into complementary slots 52 provided in the hub 51 of the knob. As best illustrated in FIGURES 2 and 3 of the drawings, the outer surface of the hub 51 is rotatably supported in the aperture 20a preferably provided with an inwardly turned peripheral flange 20b for increasing the bearing surface. With the above described arrangement, rotation of the knob 50 rotates the driver for wiping the contact buttons 33a and 33b intermediate the ends of the arcuate resistance element 16 and the contact buttons 35a and 35b against the top surface of the collector ring 17 thereby providing the proper resistance in the circuit of the hearing aid and, accordingly, controlling the volume thereof.

For the purpose of biasing the knob 50 away from the front surface of the cover 20, an apertured biasing or thrust washer 53 of dished configuration is positioned over the hub 51 between the knob 50 and the front surface of the cover 20. To control the distance between the knob 50 and the driver 40 and thereby alter the tension of the thrust washer 53, a screw 54 threadedly engages the inner bore 45 of the driver 40, the head 54a of the screw being disposed in a centrally disposed counter sunk bore 55 of the knob 50. As will become apparent from the following description, an annular head 46 integrally connected to the driver 40 is biased by the thmst washer 53 against a flexible insulating membrane 56, of nylon, Bakelite or polychlorotrifluoroethylene, mounted against the inner surface of the cover 20. Rotation of the screw 54 increases or decreases the axial distance between the knob 50 and the driver 40 for decreasing or increasing the biasing force of the annular bead 46 against the sealing surface of the flexible insulating membrane 56. By properly controlling the curvature of the annular bead engaging the flexible insulating membrane, various ranges of rotational torque are obtainable. Simultaneously with the adjustment of the rotational torque, the resistance element and the contactor are sealed from atmospheric and foreign elements exterior of the housing by the ann'ular bead 46 and the flexible insulating membrane. After the rotational torque of the control has been set to a predetermined value and the control has passed inspection, the dab 57 of epoxy cement is deposited over the head 54a of the screw 54 for fixedly securing the screw 54 to the knob 50.

Generally the angular rotation of the driver is limited to prevent the contact buttons 36a and 33b of the contactor 30 from wiping past the ends of the arcuate resistance element 16. To this end, the lower portion of the cylindrical wall 12a of the housing extends forwardly beyond the peripheral lip of the cup-shaped member 12 to form a stop member 58, and suitable reinforcing material is added to the inner surface of the cylindrical wall 12a adjacent to the stop member 58 for increasing the strength thereof. The stop member 58 projects through a slot 200 in the cover 20 and epoxy cement is applied around the edges of the slot 20c for sealing the cover 20 to the stop member 58. As shown in FIGURES 2 and 3, the stop member is received in an arcuate slot 59 communicating with the inner surface of the knob 50, the angle of rotation of the driver 40' and the contactor 30 depending upon the arc of the slot. Thus as the knob is rotated in either direction, the stop member 58 engages one of the ends of the arcuate slot 59 and limits further movement of the contact buttons of the contactor.

In view of the detailed description included above, the operation of the present control will readily be understood, and no further discussion is included herewith. It will be appreciated that suitable teeth or serrations are provided on the periphery of the knob 50 for improving manual gripping of the knob.

While there has been illustrated and described what is at present considered to be a preferred embodiment of the present invention, it will be appreciated that numerous changes and modifications are likely to occur to those skilled in the art, and it is intended in the appended claims to cover all those changes and modifications which fall Within the true spirit and scope of the present invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A variable resistance control comprising a cupshaped member of electrically insulating material having a base and a cylindrical wall, an arcuate resistance element carried by the base, a collector ring molded to the base adjacent to the resistance element, a pair of terminals molded in the base, each of the terminals having a distal end projecting outwardly of the base and an inner end connected to one end of the resistance element, a cover closing the open end of the cup-shaped member, said cover being provided with an aperture, a flexible apertured membrane disposed against the cover, a driver rotatably journaled in the base, a contactor carried by the driver engaging the resistance element and the collector ring, an annular bead integral with the driver engaging the flexible membrane disposed against the cover for sealing the inside of the cup-shaped member, a rotatable member extending into the aperture, said rotatable member being adjustably connected to the driver for varying the force of the driver against the flexible membrane and axially slideable therewith, and biasing means urging the annular head against the flexible membrane.

2. A variable resistance control comprising a housing provided with an apertured wall, a resistance element mounted in the housing, a collector ring in concentric relationship to the resistance element, a driver rotatably journaled in the housing, a contactor constrained to rotate with the driver for Wiping the resistance element intermediate the ends thereof, a flexible membrane disposed against the inner surface of the apertured wall, a rotatable member disposed outwardly of the housing, means dis posed in the aperture of the wall operably connecting the rotatable member to the driver, an annular bead integral with the driver, and resilient means external of the housing biasing the annular bead against the flexible membrane for sealing the inside of the housing.

3. In a variable resistance control provided with a housing, a resistance element supported inside of the housing, a collector ring disposed in concentric relationship to the resistance element, a driver rotatably journaled in the housing, a contactor constrained to rotate with the driver for wiping the resistance element intermediate the ends thereof, and a rotatable member operatively connected to the driver, the improvement comprising an annular bead integral with the driver, a flexible membrane having a bearing surface mounted against an inner wall of the housing, and biasing means external of the housing urging the annular head into engagement with the bearing surface of the flexible membrane.

4-. In a variable resistance control, the combination of a housing, an arcuate resistance element mounted in the housing, a driver rotatably supported in the housing, a contactor carried by the driver and adapted to Wipe the resistance element intermediate the ends thereof, said housing being provided with an aperture, a rotatable member disposed externally of the housing and operably connected to the driver, resilient means interposed between the driver and the rotatable member, and means passing through the aperture for changing the axial distance between the driver and the rotatable member for altering the rotational torque of the driver.

5. In a variable resistance control, the combination of a housing, a variable resistance element disposed in the housing, a driver mounted for rotation in the housing, a contactor carried by the driver and constrained to rotate with the driver for wiping the resistance element intermediate the ends thereof, the driver being provided with a shaft portion, a rotatable member disposed externally of the housing and provided with a complementary shaft receiving portion engaging the shaft portion of the driver, said housing being provided with an aperture, one of said portions being disposed in the aperture, a resilient member interposed between one of the walls of the housing and the rotatable member for biaSing the rotatable member away from the housing, and means for altering the axial distance between the driver and the rotatable member by changing the length of the engaged portion between the shaft portion of the driver and the shaft receiving portion of the rotatable member for varying the rotational torque of the driver.

6. The variable resistance control of claim 5, wherein a stop member projects outwardly from the housing and an arcuate groove is provided in the rotatable member receiving the stop member and limiting the angle of rotatiOn of the rotatable member when the stop member engages one of the ends of the arcuate groove.

'7. A variable resistance control comprising a housing, an arcuate resistance element fixedly secured in the housing, a collector ring mounted in the housing in concentric relationship to the arcuate resistance element, the housing being provided with an apertured wall, a flexible membrane fixed mounted against the inside surface of the apertured wall, a driver mounted in the housing, a contactor fixedly secured to the driver and adapted to wipe the resistance element intermediate the ends thereof, an annular bead integral with the driver slideably engaging the flexible membrane, and means external of the housing adjustably connected to the driver for rotating the driver and for varying the force of the driver against the flexible membrane.

8. A variable resistance control comprising a base, a cylindrical member extending upwardly of the base and integral therewith, a collector ring supported by the base, an arcuate resistance element secured to the base circling the collector ring, a terminal connected to each end of the arcuate resistance element and to the collector ring for connecting the resistance control into a circuit, a cover closing the open end of the cylindrical member, the cover being provided with an aperture, a rotatable member provided with an inwardly extending hub disposed in the aperture of the cover, a driver rotatably journaled in the housing, one end of the driver being rotatably journaled in the base and the other side of the driver being axially slideable with the hub of the rotatable member and constrained to rotate therewith, a contactor carried by the driver and adapted to wipe the resistance element intermediate the ends thereof, a thrust washer interposed between the rotatable member and the cover biasing the driver against the inside wall of the cover, and means for altering the axial distance between the rotatable member and the driver for changing the biasing force of the driver against the inside wall of the cover.

9. The variable resistance control of claim 1, wherein the driver is provided with a threaded bore and the rotatable member comprises a screw threadedly engaging the bore and rotatable externally of the housing for altering the bias of the driver against the flexible membrane;

10. The variable resistance control of claim 9, wherein the biasing means comprises a thrust washer urging the annular bead of the driver against the flexible membrane. I

11. The variable resistance control of claim 4, wherein the housing comprises, a cup-shaped member provided with a base and an open end, the arcuate resistance element is supported in the base of the cup-shaped member, an apertured cover closes the open end of the cup-shaped member, a pair of mounting ears integral with the cover extend beyond the base of the cup-shaped member for securing the cover to a panel, means on the mounting ears secure the cover to the cup-shaped member, and means are provided for preventing relative rotation between the cup-shaped member and the cover.

12. A variable resistance control comprising a hous ing provided with a wall having an aperture therein and a base in spaced parallel relationship to the wall, a resistance element fixedly secured in the base of the housing, a driver provided with a pair of spindles and a threaded bore, the spindles being rotatably journaled in the aperture of the wall and the base of the housing, an electrically insulating membrane mounted against the inner surface of the apertured wall, a knob spaced from the housing and provided with a hub rotatably journaled in the aperture of the wall and slideably engaging one of the spindles of the driver, biasing means urging the driver against the flexible membrane, and a screw threadedly engaging the bore of the driver whereby rotation of the screw with respect to the driver alters the axial distance between the knob and the driver for changing the pressure of the driver against the insulating membrane for preadjusting rotational torque of the driver.

13. In a variable resistance control having a housing defined by a pair of spaced end walls and a central portion, a resistance element supported inside of the housing, one of the end walls being provided with an aperture, a collector ring disposed in concentric relationship to the resistance element and provided with a center opening,

I a driver having a threaded bore rotatably journaled in the center opening of the collector ring, and a knob external of the housing slideably connected to the driver, the improvement comprising an electrically insulating membrane mounted against an inner end wall of the housing, means biasing the driver against the membrane, and a screw passing through the aperture adjustably connecting the knob to the driver whereby rotation of the screw in the threaded bore of the driver alters the pressure of the driver against the membrane for changing the rotational torque of the driver and simultaneously maintaining the inside of the cover sealed.

14. The variable resistance control of claim 13, wherein the housing comprises a cup-shaped member and a cover, and a pair of mounting ears integral with the cover extend rearwardly beyond the end wall of the cupshaped member for mounting the cover to a panel.

15. The variable resistance control of claim 14, wherein the cup-shaped member is provided with a plurality of peripheral shoulders defining a pair of slots receiving a portion of the mounting ears thereby restricting relative rotation between the cover and the cup-shaped member.

References Cited UNITED STATES PATENTS 2,740,027 3/1956 Budd et a1. 338197 2,201,686 5/1940 Marsten 338-484 X 2,814,702 11/1957 Mucher 338184 X 2,909,749 10/ 1959 Barden et al 338-463 3,119,089 1/1964 Murry 338202 X 3,124,775 3/1964 Hamelberg 338-163 3,193,786 7/1965 Moore et al 338164 3,197,726 7/1965 Hulbert 338--184 X 3,237,140 2/1966 Barden et al 338184 X RICHARD M. WOOD, Primary Examiner.

I. G. SMITH, Assistant Examiner. 

2. A VARIABLE RESISTANCE CONTROL COMPRISING A HOUSING PROVIDED WITH AN APERTURED WALL, A RESISTANCE ELEMENT MOUNTED IN THE HOUSING, A COLLECTOR RING IN CONCENTRIC RELATIONSHIP TO THE RESISTANCE ELEMENT, A DRIVER ROTATABLY JOURNALED IN THE HOUSING, A CONTACTOR CONSTRAINED TO ROTATE WITH THE DRIVER FOR WIPING THE RESISTANCE ELEMENT INTERMEDIATE THE ENDS THEREOF, A FLEXIBLE MEMBRANE DISPOSED AGAINST THE INNER SURFACE OF THE APERTURED WALL, A ROTATABLE MEMBER DISPOSED OUTWARDLY OF THE HOUSING, MEANS DISPOSED IN THE APERTURE OF THE WALL OPERABLY CONNECTING THE ROTATABLE MEMBER TO THE DRIVER, AN ANNULAR BEAD INTEGRAL WITH THE DRIVER, AND RESILIENT MEANS EXTERNAL OF THE HOUSING BIASING THE ANNULAR BEAD AGINST THE FLEXIBLE MEMBRANE FOR SEALING THE INSIDE OF THE HOUSING. 